(ii) sin(a+h)−sinah=cos(a+h2)⋅sin(h/2)h/2\boxed{\frac{\sin(a+h)-\sin a}{h}=\cos\left(a+\frac{h}{2}\right)\cdot\frac{\sin(h/2)}{h/2}}hsin(a+h)−sina=cos(a+2h)⋅h/2sin(h/2)